This commit adds some better handling around the snapshot restore and delete commands for the virtualbox provider. If a user attempts to restore from a vm that does not exist, instead of exiting 0 it will raise an exception saying the virtual machine has not been created yet. Addtionally, if a user attempts to restore from a snapshot id that does not exist, instead of printing a complicated exception from the virtualbox cli tool, it prints a more useful error message telling the user that the snapshot does not exist.
Vagrant Core Plugins
These are plugins that ship with Vagrant. Vagrant core uses its own plugin system to power a lot of the core pieces that ship with Vagrant. Each plugin will have its own README which explains its specific role.